A variety of fine particle dry powders such as baking products (e.g., flour, baking powder, baking soda, and powdered sugar) are packaged in paper or cardboard containers. Paper and paperboard containers permit the above products to be packaged with a lower content of air than would occur with different containers such as plastic bags. Such containers are highly porous and/or are self venting. The above baking products are not packed in plastic bags because plastic bag containers trap air that is difficult to evacuate from the plastic bag without evacuating a portion of the baking product in the plastic bag at the same time.
Conventional paperboard and paper containers, however, have numerous deficiencies. For example, the traditional paper container for flour can be damaged or infiltrated by numerous environmental factors. The paper tends to absorb moisture that contacts the paper. The moist paper becomes a breeding ground for mold and mildew that can damage the flour. The moisture also causes the paper fibers to expand and weaken, making it easier for the paper container to tear open. The paper container is also susceptible to insect infestation. Numerous types of insects will easily chew completely through the paper. In addition, because of the porous nature of paper, various odors and particles can pass through the paper resulting in a less fresh flour product. The porous nature of the paper also permits moisture to migrate out from the flour product to outside the paper container. This is an especially acute problem when flour is stored in an environment having a low humidity or dew point level. Flour normally has a moisture content of about 14%. In order to compensate for the expected loss of moisture, flour producers actually overfill the paper container to ensure that the product still weighs the amount listed on the packaging after being exposed to a drier environment and losing a certain amount of moisture content. Although only a small amount of overfill is required, the cost to the manufacturer is very significant when you consider the millions of tons of flour that is packaged and sold in the world. Moreover, environmental desiccation can adversely affect the flour's baking properties thereby undesirably leading to a consumer perception of low or poor flour product quality.
The paper containers are also not desirable from a shipping standpoint. When the paper container is filled with flour, the flour becomes aerated, taking up a greater volume of space. The additional space taken up by the aerated flour costs money. In addition, the general rectangular/cylindrical shape of the flour container causes problems with stacking and moving. Complicating the stacking problem is the uneven distribution of flour within the paper container. For example, a first paper container of flour is stacked on top of a second paper container of flour. The weight of the first container causes a downward, compressive force on the second paper container of flour. The air in the second paper container, however, cannot completely escape from the sealed paper container. The result is that the second paper container becomes an unstable, bulging foundation for the first paper container. The problem is exacerbated when a third paper container of flour is stacked on top of the first paper container of flour, creating additional downward force on the second paper container. Unstable stacks of flour containers can be extremely dangerous during shipping. Shifting loads can tip over tractor trailer trucks or fall on top of workers.
Conventional paper flour containers are also not desirable for consumer use. Paper containers are not resealable, thus, the consumer must place the contents into another container in order to prevent the contents from spilling, absorbing moisture or bug infestation. Opening paper containers of flour can also be messy. The conventional method of sealing a paper container involves gluing or seaming a series of folds at the top and bottom of the container. During the sealing process, flour becomes caught between the various folds. When the paper container is opened at the top, the flour caught in the folds, spills onto the counter. Also, such paper flour containers lack an easy-to-open feature. In addition, the shape of the paper container is not generally conducive to baking. Specifically, the tall cylindrical shape is not stable and tends to fall over easily. Moreover, the top end of the container that is opened to access the flour usually folds back onto itself, making entry and removal of a scoop difficult. The shape of the paper container is also a difficult shape to handle with only one hand. The paper container also makes it nearly impossible to tell how much flour is left in the paper container without actually having to look inside the container.
The conventional paper flour container is also not economically efficient to the consumer. Flour becomes trapped in the bottom folds inside the paper container, depriving a consumer of some of the flour product purchased. In addition, similar to the problem faced by the shipper, the consumer has difficulties stacking paper containers of flour. Even if the consumer transfers the flour in the paper container to a plastic bag, the flour cannot be stacked because the air trapped in the plastic bag is difficult to evacuate out of the plastic bag without evacuating some of the flour at the same time.
Paperboard packaging poses similar problems. Paperboard is susceptible to water damage. Paperboard containers, although rigid, can also cause shipping problems. The rigid shape prevents a manufacturer from evacuating all of the air out of the container. Excess space is, therefore, taken up during shipping. The manufacturer cannot evacuate all of the air out of the container, thus, after the product eventually settles, there is an air pocket inside the cardboard container. The air pocket causes a portion of the cardboard container not to be supported by the product. The lack of support allows the cardboard to be more easily dented or crushed. A crushed wall of a cardboard container can cause a load of cardboard boxes to become unstable and either shift or collapse. Paperboard containers usually do not seal close, but are closed with a flap. The lack of a tight seal allows moisture, mold and insects to penetrate the container. In addition, cardboard containers are not transparent. This prevents a consumer from being able to view whether the container is full without having to open the container.
Plastic bags have long been used for dry powders having a generally larger particle size such as conventional granular sugar and ready-to-eat breakfast cereals. However, such bags generally include at least one opening such as a notch, pin hole or air channel to provide for air escape during packaging to provide an aspirated plastic bag. Also, the air escape hole allowed for shipment of the bags over mountains/high altitudes without causing rupture or bursting.
The presence of the pinhole to allow entrapped air to escape or vent, of course, renders the containers nonsuitable for use for containing liquids. Also, such air channels, holes, etc., undesirably allow insect contamination. Also, while such pinhole containing or perforated plastic bags are useful for particulate materials having a larger particle size, such as regular sugar, such perforated containers are unsuitable for use with fine powders such as baking flour. As the plastic bag is compressed during processing to expel any entrapped air, some amount of fine flour materials can be carried along with the air through the perforations. The expelled flour dust presents numerous sanitation negatives. More importantly, airborne flour dust is highly explosive and presents an extreme safety hazard.
Imperforate conventional plastic bag containers are not practical for fine particle baking products either. Imperforate bags that have air in them are not practical for shipping. They balloon up especially at higher altitudes, are unstable and take up additional precious cargo and storage space. In order to evacuate the air out of the bag, the air is either compressed out of the bag or it is vacuumed out of the bag prior to complete sealing. With fine particles, however, some of the particles get compressed out the bag or sucked out of the bag through the vacuum mechanism. Even if the manufacturer successfully evacuates air out of the plastic container, the consumer, however, normally does not possess a vacuum device or compression device to evacuate air after opening the bag. Consequently, the consumer, after the bag has been opened, has a bulky, ballooned-up bag.
Conventional containers for holding fine particle baking products are not desirable for shipping, storage or consumer use. A container for holding fine particles that can be sealed and resealed, but can easily have air evacuated out of it without removing the fine particles, is desired.
The present invention is a further improvement in the containers for storing fine particles disclosed in co-pending commonly assigned U.S. Ser. No. 09/135,319 (filed Aug. 7, 1998; attorney docket GMI 5144) entitled "Container For Storing Fine Particles" which is incorporated herein by reference. In the prior invention, plastic bags are provided with one or more macroscopic apertures or openings for exhausting of extrapped air. overlaying the apertures are air permeable but particulate impermeable layers, preferably mounted on the interior surface of the bag. Such a construction provides for desirable release of entrapped air while preventing escape of the contained particulate material or ingress by insects.
The present invention is also a further improvement in the improved containers for storing liquid or dry material such as flour, disclosed in co-pending commonly assigned U.S. Ser. No. 09/135,318 (filed Aug. 7, 1998, attorney docket GMI 5145) entitled "Container For Storing Fine Particles" which is incorporated hereby by reference. In that invention, a multiplicity of microscopic pores substitute for the single or smaller number of macroscopic openings or notches of the prior invention. In a further improvement, the previously required impermeable layer overlaying the macroscopic aperture can be eliminated. In addition to the structural differences in the present containers, the present invention provides important advantages in the ease and cost of fabrication.
The present invention provides further improvements in plastic bags for holding materials, especially those improved plastic bags for containing fine particles such as baking flour. The improvement comprises providing plastic bag containers for such materials having an external surface characterized by a coefficient of friction of about 0.4 to 0.5. Bags can be fabricated from film materials having the desired coefficient of friction. In other variations, bags can be treated by applying a topical coating to impart the desired characteristic.